NII Technical Report (NII-2008-009E)

Title Asynchronous Pipeline Controller Based on Early Acknowledgement Protocol
Authors Chammika MANNAKKARA , Tomohiro YONEDA
Abstract A new pipeline controller based on Early Acknowledgement protocol is proposed for bundled-data asynchronous circuits. The Early Acknowledgement protocol indicates acknowledgement by the falling edge of the acknowledgement signal in contrast to the 4-phase protocol which indicates it on the rising edge. Thus, it can hide the overhead caused by a resetting phase of the handshake cycle. Since we have designed our controller assuming several timing constraints, we first analyze the timing constraints under which our controller correctly works, and discuss the appropriateness. Advantages of employing the Early Acknowledgement protocol in a pipeline controller is demonstrated by comparing performance of the proposed controller with that of two other pipeline controllers, namely, a very high-speed 2-phase controller and an ordinary 4-phase controller, both analytically and experimentally. We have obtained interesting results in the case of a non-linear pipeline with a Conditional Branch operation. Since Early Acknowledgement protocol employs return-to-zero control signals like 4-phase protocol, our controller for Conditional Branch operation is simple in construction identically to the 4-phase controller. A 2-phase controller for the same operation needs to have a little complicated mechanism to handle the 2-phase operation due to non-return-to-zero control signals. For such simplicity of the implementation, our controller has a slightly better performance compared to the 2-phase controller when each stage has a processing element. Thanks to the superiority of the Early Acknowledgement protocol, our controller substantially outperforms the 4-phase controller too.
Language English
Published Sep 24, 2008
Pages 18p
PDF File 08-009E.pdf

NII Technical Reports
National Institute of Informatics